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Author Topic: Station Grounding  (Read 1044 times)
KB1FXL
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« on: July 18, 2001, 09:06:32 AM »

All my product documentation (antenna/rig) talks about connecting the equipment to a good earth ground. It also mentions keeping the heavy gauge wire as short as possbile.

My shack is on the second floor and my antenna is on the roof. The house earth ground is as far away as it can get from my shack. Using heavy gauge wire at this length is going to make a better antenna than a ground.

How do people go about solving this problem. Short of disconneting everything when the rig is not in use, I'm at a bit of a loss.
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K9UW
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« Reply #1 on: July 18, 2001, 10:30:18 AM »

Hello!

Try a "zero length" coaxial RF ground.  You can make this yourself with any conventional coaxial cable that runs from your rig's ground terminal to your ground rod.  The trick is to use two .001mf 1kv disc capacitors, one at each end, soldered between the shield and the center conductor.

I used this technique years ago, after reading about it in 73 Magazine, and found that it worked very well.  Sure wish I could find that article again, as it was excellent!

You can visit The WireMan's web site at http://www.thewireman.com/ground.html, where he offers a coaxial ground "kit" that appears to consist of the disc capacitors you'll need.  The kit is one dollar.

Another option is to create counterpoises, one cut at 1/4 wavelength for each band you operate on, and attach those wires directly to the ground terminal on your rig.  Snake the wires around the perimeter of the shack to keep them from mixing with your feet, etc.

Still another option is to obtain an "Artificial Ground" which, as I understand it, is a tuner that produces the electrical equivalent to the aforementioned quarter wavelength counterpoise.

Normally, I don't consider contributing to these discussions because my technical knowledge is limited and there is always someone who knows more than I, but your question cried out for an answer and I decided to stick my neck out.  I'm confident in my knowledge on this occasion, however.  Give one or more of these options a try and I'm sure you'll find one that works.

Remember:  "Who needs the frustration of a career when your hobby is Ham Radio?"

73, de

Mike, K9UW
Amherst, WI
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KA1DBE
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« Reply #2 on: July 18, 2001, 10:33:38 AM »

To ground or not to ground.....that is the true question.....well, I have been operating for about 22 years and I don't think I have ever had my equipment grounded.  I can hear the "purist" groaning but it has never really been a problem for me.  

Now, if you have RF in your shack or a lot of computer hash in your reciever than I would think about grounding.  Instead of running a really long ground (which would become resonant at some point), use a counterpoise.  Make it a 1/4 wave for the band of interest (or use rotor cable and make it for all the bands of interest) and that will give your rig something to work against.

Well, I am looking forward to all the responses to this...good luck and Best 73s.....

Jeff, KA1DBE/4
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WB2WIK
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« Reply #3 on: July 18, 2001, 10:56:35 AM »

This subject has been repeatedly beat to death, and opinions vary as the weather.

I've been actively hamming for over 36 years, run all bands from 1.8 through 1296 MHz, at power levels including 1500W output, and never use a "station" ground -- actually, never have.  In order to define the kind of ground required, you'd need to first define its purpose.  Its specific purpose.  Give up?  So do I.

You didn't mention what kind of antenna(s) you're using, or what frequencies.  Antennas which are resonant, well matched, and fed with coaxial cable will not produce any "RF in the shack" problems...they can't.  All the RF produced by the transmitter is carried by the outer surface of the inner conductor, and the inner surface of the outer conductor, of the coaxial cable and no current flows elsewhere.  The purpose of a station ground in this situation eludes me, and eludes everybody else, too.

A station ground will be very helpful if voltage-fed, high impedance, mismatched antennas are used.  In these situations, it is common for RF voltage to appear on equipment chassis and everything connected to same, including microphone lines, key lines, etc.  Ouch.  This can not only create a hazard (RF burns and bites) but is likely to cause equipment malfunction.  Now, a station ground of some sort is called for, and its installation and application can be tricky.  Tuned counterpoises, phantom grounds, etc, etc, can all help a lot, and most do not require a direct earth connection to be effective.

A "safety" ground, that is one which creates an earth return from equipment chassis, which will short out the AC mains and ultimately (hopefully) blow a fuse or trip a circuit breaker in the event of a power supply malfunction, or drain leakage current back to earth to prevent operator risk, should be provided by your 3-wire power cord.  A secondary "safety" ground is always a good idea, and it needn't be an effective RF ground -- just a conductor from equipment to earth, capable of handling primary current long enough to trip a breaker.  #14 copper is sufficient, as most AC mains house wiring is also #14 copper.  Such a ground should be periodically checked for continuity and true earthing.

A "lightning" ground is something that should NEVER be connected to equipment in the home!!!!

So, that leaves the "RF" ground, which, in cases employing 50 Ohm matched antennas fed with coaxial cable, is unnecessary.  There are circumstances where an RF ground will be helpful, but those are as described above; typically, where non-resonant antennas, or antennas fed with unshielded cable, are employed...and those will also normally require an external antenna tuner.

73 de Steve WB2WIK/6

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AC5E
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« Reply #4 on: July 18, 2001, 04:27:15 PM »

 HI: If you don't have RF in the shack, you really don't need an RF ground. But a safety ground is required by the electrical code and a lightning ground is probably required by your insurance company. Especially if you are in an area like mine, with almost daily thunderstorms.
  Almost any reasonable size wire running to ground, and preferably to the ground rod that is connected to your meter base, will do for a safety ground. Even #18 will trip a 15 amp breaker before it melts.
  And of course, the lightning ground should be completely independent of your house grounding. But there's not a thing wrong with installing a good lightning ground, consisting of at least two and preferaby three or more 8 foot ground rods on 8 foot centers tied together with #6 copper or larger: and with a lightning arrestor (ICE, Alpha Delta, etc.,) for each coax solidly bonded to that ground. If you do that, your RF ground and your lightning ground are one and the same and far removed from your shack.
  73  Pete Allen  AC5E
   
 
 
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NB6Z
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« Reply #5 on: July 18, 2001, 04:52:18 PM »

Try it without the ground! Unless you are planning an end fed zep type wire antenna, you probably have no real need for an RF ground. If you have RFI in the shack, you can try some of the tricks described above.
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WB2WIK
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« Reply #6 on: July 18, 2001, 05:29:39 PM »

Good comments; but beware the "lightning ground" issue, it's a toughie.

I don't know about Pete's insurance policy, but mine states that the prevailing code must be followed; the prevailing code is that no lightning grounding system is allowed inside the building, not even a conducted one.  The idea of using paralleled ground rods, etc, and bonding them to spark-gap or similar devices outside the shack certainly has merit and might help prevent lightning damage, especially EMP damage, but such a remote grounding system is not a real "RF" ground, because it's not attached to the station equipment needful of grounding by any means other than the relatively high impedance of the coaxial cable braid.

An "RF" ground must be one located directly at the transmission source.  If you tie the shield of a coaxial cable transmission line directly to earth with a "zero" impedance ground located 1/4-wavelength away from the transmitter, this "zero" impedance ground is transformed to an "infinite" impedance ground, or in other words, no ground at all.  The same thing occurs at all odd integers of 1/4-wavelength.  If multiple amateur bands are intended to be covered, it is nearly impossible to avoid a situation where ground impedance won't be very high at some frequency.

Thus, phantom grounds, or artificial grounds, or multiply tuned counterpoise elements, or some such system is nearly required for actual "RF" grounding when multiple bands are operated.  Assuming any RF ground is needed at all!  My contention is that an RF ground is superfluous in most real world amateur applications, where coaxially fed, resonant and matched antennas are utilized.  On those occasions where longwires and such are being used, unless the transmitter and antenna tuner happen to be literally sitting on earth and are bonded with some zero-impedance path to the earth they're sitting on, achieving an "earthed" RF ground is essentially impossible, so we do what we can.  Half-wavelength, resonant ground wires that are actually earthed at the far end and tuned for each band used; or quarter-wavelength, resonant counterpoise wires that are intentionally floating above earth at the far end and also tuned for each band used, work pretty well.

73 Steve WB2WIK/6
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AC5E
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« Reply #7 on: July 18, 2001, 09:37:53 PM »

 Well, my local building code requires a single ground, a single point of contact if you will, for all commercial electrical "entrances" in a home. That includes the electrical entrance, telephone, and CATV cable. It does NOT include outside TV antennas or ham antennas. While my local codes do require electric range and hot water heater cases be "grounded" to that single entrance "ground," ham rigs are considered small appliances that need not be connected to that ground.
  And, as a point of interest, the 6 foot ground rod the power company installed when they ran power to the house is grossly inadequate for any sort of electrical ground. But it's required!
  My insurance carrier requires "good engineering practice" for external radio and TV antennas, towers, etc., etc.. Their definition of good engineering practice includes an "adequate" ground system with sufficent grounding capicity to dissapate a substantial lightning stroke; and at least one approved lightning arrestor in each and every transmission line and control cable; installed between any and all fixed antennas and the house. Not the equipment in the house, between the antennas and the house. My agent essentially ordered me to follow the Polyphaser book when installing any tower.
  Now, a lightning stroke has a very short rise time. So a lightning stroke contains RF. A lot of RF. RF that is almost literally "DC to Daylight." So it should be obvious that any ground system "adequate" to short stop a lightning stroke must have a very, very low impedance to ground. In fact, for all intents and purposes, an "adequate for the purpose" ground must be ground.
  So where does RF on a transmitter case come from? Since TVI reared it's ugly head back in the late 1940's and made us shield our transmitters, RF in the shack comes in the shack on transmission lines and control cables.
  If those transmission lines and control cables are forced to be at ground potential some 30 feet from the house they must also be at ground potential at the rig. No matter how much RF may be on them between the arrestors and the antennas.
  Therefore, neither the length or the impedance of the coax shield between the rig and the lightning arrestors enter in the equation at all. There should be esssentially NO RF on that shield, because any RF inside the arrestors is confined to the inside of the coax. And if you do find RF in the shack, you are being warned that your lightning ground is inadequate.
  73  Pete Allen  AC5E
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WB2WIK
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« Reply #8 on: July 19, 2001, 10:48:49 AM »

The problem with that thinking is that it precludes use of other transmission line systems, besides coaxial cable.  When coaxial cable is terminated by a load having the same impedance as the cable, there won't be any RF on the outer surface of the cable's shield, and there won't be any RF in the shack, at least not on the equipment chassis.  So, we're in total agreement there.  Except that in my statement, it doesn't matter whether the cable's shield is connected to an earth ground outside the shack or not -- there still won't be any RF in the shack.  Where could it come from?

However, since a "station ground" is really only a requirement when using NON-coaxially fed antennas such as balanced lines, or no line at all (end-fed wire), this is a predicament.  There's no place you can effectively ground the "feedline," inside or outside, other than for DC purposes, through an RF choke or system of RF chokes.  But a low-impedance ground is prohibited by design.

For lightning purposes, "transi-trap" type devices, or the old methodology of using spark plugs on the feedlines and antenna wires, with one plug element well earthed and the other directly attached to the line or antenna, have merit.  I've used such systems myself, and they are in common use at commercial broadcast facilities.  But in these cases, there is no direct connection between earth and the station equipment, or if there is one, it is coincidental and not intentionally designed to perform any purpose.

So, what's a ham to do when he wants to use an end-fed wire antenna with a tuner in the shack, and wants an "RF ground" for his station?  My entire previous discussion related to this situation.

73 Steve WB2WIK/6
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AC5E
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« Reply #9 on: July 19, 2001, 12:27:48 PM »

   We are getting a pretty good discussion going here, Steve. If we keep this up we will all learn something. Which is the purpose of this forum.  
   Out at the farm I use Amidon's 6:1 and 9:1 baluns to feed ladder line - and two half rhombics (vee beams) and a long wire outboard of my lightning grounds. That is - either rig, coax, lightning arrestors, balun, ladder line, antenna - or one side of a 9:1 balun is tied to a long wire, the other side is attached to the lightning ground.
   By the way, the lightning ground at the farm is 40 feet of oil rig drill stem driven 15 feet below the permanant water table. I don't know how many mega-amps it would take to destroy that ground, but Buck and I tend to build "hell for stout." It saves trouble in the long run.
   The setup on top of the drill stem does not look all that pretty, particularly the spark gaps at the balun terminals,  but it does work. And the system has taken at least two lightning hits that destroyed the ladder line without damaging either the baluns or the rigs.  
    73 Pete Allen  AC5E
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WB2WIK
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« Reply #10 on: July 19, 2001, 01:38:28 PM »

Holy cow, that's heavy hardware for sure.

I should smugly reply that here by the southern California seashore, lightning is such a rarity that I can only recall actually seeing it once, in 13 years.  I should smugly say that.  But I'll resist the temptation!

<smirk>

73!

Steve WB2WIK/6
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RobertKoernerExAE7G
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« Reply #11 on: July 20, 2001, 05:50:47 AM »

I've never lived anywhere where I could get an 8 foot rod into the ground.  Even out here in the dessert, you are lucky to get an 8 foot rod all the way into the earth.  Back in New England, just finding a place to get 4 foot rod into the ground was real hard.  I'd usually wind up with about 4 or 5 four footers in the ground, with none of them all the way into the earth.

When I first became a ham, I had a second floor radio room.  Of course, I ran a 22 gauge wire from the back of my FT101EX to a ground rod.  But, if I touched the metal box surrounding my watt meter, it would bite me.  I was using a traped inverted vee.

When I moved to another house, I never grounded my rig, and never got bit again; and haven't grounded my rig or amplifiers to an earthen ground since then.

I live where the storm cells roll through the area constantly during the summer, moonsoon season.  When I'm not using my antennas, they are disconnected.  the amp is only plugged into AC when I use it.  My tower is grounded, 4 eight foot ground rods driven as far as they would go into the earth, between 3 feet and 6 feet.  The tower was instaled here in 1989.  I bought my amp in the mid 80's; been haming for 22 years.  Not grounding my rig and amp seems to have worked so far?
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AG4DG
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« Reply #12 on: July 20, 2001, 09:02:35 AM »

The need for an RF station ground (as opposed to the ground plane, DC ground, and lightning ground) is a MYTH.  I delved into this issue myself and explained what I learned at:
http://www.jasonhsu.com/ham_radio-technical.html

I should also note that the antenna expert in our club (who has been a ham since 1952) does NOT attach anything to the grounding screws of his transceiver or tuner.
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KA2QFX
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« Reply #13 on: July 20, 2001, 04:42:10 PM »

Oh, I see we're discussing grounding again.  Well, opinions and technigues may vary but physics and legal requirements tend to be pretty constant.  WIK's comments are, as usual, quite correct. If your transmission lines and antennae function as they should no station ground should be required, or desired.
But since we live in an imperfect world a station ground, RF or otherwise, is sometimes desirable. Defining, let alone quantifying, such a thing is another matter.  

For yet another free opinion, whose application has served me well over many years of operating, please read the article at the link below.

http://www.bridgeport.edu/~msedutto/grounds.html

Good luck and good operating.

73,
Mark
KA2QFX
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KD5MAW
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« Reply #14 on: July 20, 2001, 06:33:20 PM »

Driving a standard copper-clad steel rod through the caliche around here is next to impossible. So I solder a hose connector to a 3/4"x10 foot copper pipe and water drill the suckers in. No sweat.
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